So I really like to validate email addresses using Email::Valid. But yesterday, I got a bug report. Some system was sending emails to another system with addresses containing a space right after the @. That other system was totally unable to deal with those.
"But I do email address validation" I thought. "Not just with a stupid regular expression like
.+\@.+, but with
Email::Valid". So I added a test to our suite and sure enough, that new test failed.
Lesson learned: Read the documentation of the modules you use.